Burglar alarm



Oct. 15, 1929. w, BAKER 1,731,605

' AAAAAAAAAAA RM Filed Aug. 24, 1928 Patented Oct. 15, 1929 PATENT OFFICE WILLARD L. BAKER, OF SAN ANTONIO, TEXAS LBURGLAR ALARM Application filed August 24, 1928.

This invention is an attachment for door knobs by the use of which an alarm will be sounded whenever the knob spindle is rotated in an effort to open the door from the outside so that the occupants of a room or building will be notified and unauthorized entrance will be frustrated. The invention is illustrated in the accompanying drawing and will be hereinafter fully set forth.

In the drawing:

Figure 1 is a view of a door having the invention applied thereto, the knobs and the attachment being shown in top plan and the door and door frame being shown in horizontal section;

Fig. 2 is a vertical section on the line 22 of Fig. l, and

Fig. 3 is a transverse section on the line 33 of Fig. 2.

The door, indicated at 1, may be of any known or approved form and the knobs 2 are of standard dimensions and configuration, the knobs being disposed at opposite sides of the door and secured upon the knob spindle of the lock in any desired manner.

The device of my. invention comprises a circular shell having a body plate 3 and an annular rim 4L around the periphery of the body plate and disposed at a right angle to the plane of the plate. At intervals in the extent of the rim 4 transverse corrugations 5 are formed therein whereby beads or pro jections are produced upon the inner circumference of the rim, as clearly shown in Fig. 2. At the center of the plate 3 is a boss 6 which is adapted to receive the inner end of an attaching screw 7 whereby a bell 8 may be secured within the rim and carried by this bell are diametrical arms 9 which have their ends turned inwardly from the bell, as shown at 10, whereby they are adapted to engage over a door knob, as shown clearly in Fig. 1, it being noted that the projecting ends 10 of these cross arms are arcuate in form so that they will fit closely around the knob and will not be apt to be accidentally dislodged. The arms are resilient that they may be easily pushed over the knob and effectually engage the convex surface of the same to re- 59 tain the device thereon. At the same time Serial No. 301,900.

made to open the door from the outside, the

rotation of the outer knob will, of course, be transmitted directly through the knob spindle to the inner knob and from the inner knob to the shell inasmuch as the spring arms which clip the device to the knob will hold the device so firmly that any movement of the knob will necessarily be transmitted to the bell and the shell. Rotation of the shell will, of course, impart a spinning motion to the ball and the projections on the inner surface of the rim will throw the ball forcibly against the bell so that the latter will be sounded and the attention of the occupants of the building or room will be attracted.

My device is' obviously simple in construction and may be produced at a very low cost and very easily applied to a knob whenever its use is desired. It maybe easily removed when free access to the room is to be permitted and when in use will not detract from the appearance of the door nor interfere in any way with the usual operation of the door or the knobs.

Having thus described the invention, I claim:

An attachment for door knobs comprising a bell shaped to fit over the outer end of the knob, resilient arms secured to the bell and adapted to engage around the knob, a shell consisting of a circular plate and an annular rim, the rim being provided with projections on its inner circumference, means for securing the shell to the bell, and a ball housed within the shell and between the same and the bell and freely movable in the shell.

In testimony whereof I afiiX my signature.

WILLARD L. BAKER. a 3. 

